Over eight million Veterans receive care from VA; many of these Veterans have complex healthcare needs because of multiple chronic conditions, the need for highly specialized care, use of multiple healthcare systems, and long travel distances to the nearest VA facility. VA has committed to providing patient-centered care to address some of these challenges through the implementation of a medical home model. Patient engagement is one of the foundational elements of a successful medical home model; this engagement often involves extensive interaction with and management of personal health information. Effective personal health management, including information sharing, has the potential to improve self-management, increase provider-patient communication, increase coordination, and empower patients to become more engaged in their care. Although many people manage their personal health information using paper-based systems, improvements in technology and increased access to the internet have created new opportunities for patients to manage their information electronically. In 2003, VA nationally launched their web-based personal health record portal, My HealtheVet. There are varying levels of user access that can allow patients access to a variety of features from health educational materials to lab tests and results. Veterans also have the ability to download their personal health record using the Blue Button and send secure messages to the primary VA healthcare provider. As of September 2013, there were 2.49 million registered users; this was an increase of approximately 27% from the prior year. Over eighty percent of registered users were VA patients (2.02 million), and 1.33 million had premium accounts which allow them to opt in to secure messaging and access data from the VA electronic medical record. There were 881,000 Blue Button users and 4.7 million Blue Button downloads. Approximately 790,000 VA patients have opted in to secure messaging; in September 2013, over 600,000 messages were initiated. These numbers demonstrate the significant number of VA patients who use My HealtheVet, and that the number has increased substantially over the past year. In the proposed study we aim to (1) assess the association between My HealtheVet use and VA costs and utilization, focusing specifically on prevalence of missed appointments, hospitalizations and use of secure messaging, and (2) assess the association between My HealtheVet use and dual use of VA and Medicare services, focusing specifically on duplication of tests and medication in dual users. [To accomplish our aims, we propose to examine changes in utilization and cost variables over time for new My HealtheVet users in FY2012. The comparison group will include a sample of Veterans who have had at least two encounters at a VA facility during FY2012 and who are not My HealtheVet users. To address potential endogeneity, we will use an instrumental variable approach.]